Learn Spanish (Latin America): El lago no es más profundo que el océano.

In English, we often add '-er' to short adjectives to compare things, like changing 'deep' to 'deeper'. Spanish doesn't have an '-er' ending. Instead, you always use más (more) plus the adjective. So, más profundo literally means 'more deep'.

How do you say 'than' in this comparison?

In Spanish comparisons, 'than' is translated as que. You will use the pattern más + [adjective] + que (more... than) or menos + [adjective] + que (less... than) very often!

Why does the adjective profundo end in -o here?

Adjectives must match the gender of the noun they describe. Because the first subject, el lago (the lake), is a masculine noun, the adjective must be the masculine profundo. If we were comparing a pool (la piscina, feminine), we would say más profunda.

Where does the no go when making a comparison negative?

The negative word no always goes right before the main verb. In this sentence, it goes before es (is). You say no es más profundo (literally 'not is more deep'), rather than putting the no next to más.